Local site conditions and seismic risk assessment of historic buildings

摘要

The objectives of the Istanbul Seismic Risk Mitigation and Emergency PreparednessrnProject are to improve Istanbul’s preparedness for a potential earthquake. Within this framework "RiskrnAssessment of Cultural Heritage Buildings" was designed to address the vulnerability of cultural assets,rnspecifically buildings with global cultural heritage value. One of the components of the project was thernvulnerability and risk assessment of 170 historic buildings of varied age, value and state of conservation,rndistributed over several square miles. Many of these buildings have public functions such as museums orrneducation establishments. Among the most famous are Topkapı Palace and Hagia Irene museum. After arndiscussion of the choice of the most appropriate earthquake scenario, the methodology used for assessingrnthe effects of local site conditions on the seismic performance of selected cultural heritage buildingsrnis presented. The purpose is to estimate the earthquake characteristics on the ground surface based onrnthe probabilistic and deterministic hazard studies. The site specific elastic design spectra for each siternare then manipulated to obtain site specific nonlinear displacement spectra, so that these can be directlyrncompared with capacity curves for the buildings obtained by using mechanism approach limit state analysis.rnThe procedure for obtaining the capacity curves is described and the choice of the most appropriaternlevel of ductility and the equivalent reduction coefficient are discussed. A procedure to evaluate performancernpoints and to define safety factors based on lateral acceleration, drift or expected damage level, isrnpresented. The process of arriving at a risk evaluation and hence recommendation for strengthening orrnotherwise, is finally highlighted with respect to four comparable case studies.